A known wire-dot print head employs piezoelectric elements capable of converting electric oscillations into mechanical oscillations or magnetostrictive elements capable of being strained by a magnetic field as driving means. Since the piezoelectric action of piezoelectric elements and the magnetostrictive action of magnetostrictive elements are exactly dependent on high-frequency driving pulse signals, the employment of piezoelectric elements or magnetostrictive elements as driving means for a print head enables high-speed printing.
Although piezoelectric elements and magnetostrictive elements have the foregoing advantages, the mechanical strain of those elements, in general, is a very small value in the range of 7 .mu.m to 15 .mu.m, whereas the required stroke of the print wires of a print head is on the order of 0.3 mm at the minimum, and the stroke must be on the order of 0.5 mm to print on various kinds of recording media with a satisfactorily high print quality.
Print heads employing piezoelectric elements or magnetostrictive elements as driving means, such as those disclosed in Japanese Patent Laid-open (Kokai) No. 59-26273 and Japanese Utility Model Laid-open (Kokai) No. 63-198541, multiply the mechanical oscillations of the elements mechanically and transmit the multiplied mechanical oscillations to the print wires.
The known print heads proposed in Japanese Patent Laid-open (Kokai) No. 59-26273 and Japanese Utility Model Laid-open (Kokai) No. 63-198541 need a complicated mechanism, which requires much time and labor for manufacture, for mechanically multiplying dimensional variations of the elements and for transmitting the multiplied dimensional variations to the print wires. Accordingly, these known print heads have a high manufacturing cost and are difficult to manufacture by a mass-production process. The mechanical amplifying mechanism of the print head disclosed in Japanese Utility Model Laid-open No. 63-198541 has a displacement transmission system, including sliding components, which are abraded and thereby reduce the life of the print head.
Techniques for multiplying the oscillation of elements by a simple mechanism are disclosed in the following references.
A method disclosed in Japanese Patent Publication (Kokoku) No. 60-54191 em ploys a plurality of magnetostrictive elements and adds up the respective dimensional variations of the elements. A method disclosed in Japanese Patent Laid-open (Kokai) No. 63-144055 employs a horn for multiplying the oscillations of the elements.
These techniques disclosed in the foregoing two references, however, are capable of multiplying the oscillations of the elements only several times, and the multiplication ratios of these techniques are not large enough for printing with a satisfactorily high print quality.